Question

Why is sand used for slow cooling?

Why is sand used for slow cooling?

Answers

Answering this in contrast with your other question of "Why is water used for rapid cooling", it's because:

1) Dry sand has a conductivity of 0.15 - 0.25 W/mK, but water has a conductivity of 0.58 W/mK.

2) More importantly, it can only transfer heat away through conduction. Solids (like sand) can't carry heat away through convection, but liquids (like water) can, making heat transfer much faster.

#1